This invention relates to flame retardant/smoke suppressant additives for halogen-containing polymers such as polyvinyl chloride (PVC).
PVC is an inherently flame retardant polymer but some additives, especially plasticizers and process aids, may increase its flammability. Wire and cable in general and, in particular, plenum cable, require high flame retardancy and low smoke generation. To achieve these requirements, large amounts of flame retardants and smoke suppressants are conventionally added to PVC. Known flame and smoke retardants include such compounds as antimony oxide, molybdates and borates. However, antimony oxide is toxic, borates are relatively poor flame retardants and molybdates are expensive, factors which tend to militate against their use.
It is an object of the present invention to provide a new high performance additive which imparts excellent flame retardant and smoke suppressant properties in halogen-containing polymers.
It is a particular object of the invention to provide compositions of halogen-containing polymers such as PVC, especially PVC compositions employed as wire and cable coatings, containing a heterocyclic tin compound as a flame retardant and/or smoke suppressant additive.
It is another object of the invention to provide a flame retardant and/or smoke suppressant additive for the insulation layer of an electrically conductive wire or cable product.
It is yet another object of the invention to provide a PVC composition with largely improved heat stabilization by the addition of perchlorates.
In keeping with these and other objects of the invention, there is provided a halogen-containing polymer composition comprising a halogen-containing polymer and a flame retardant-effective and/or smoke suppressant-effective amount of heterocyclic tin compound obtained from the reaction of (i) a trisubstituted triazine compound of the general formula: 
wherein X, Y and Z each independently is a halogen atom, hydroxyl group, amine group or monovalent moiety containing at least one halogen atom, hydroxyl group and/or amine group, with (ii) a tin-containing compound selected from the group consisting of tin chlorides, tin bromides, tin fluorides, tin iodides, tin hydroxides and tin oxides.
The foregoing heterocyclic tin compound imparts excellent flame retardant and smoke suppressant properties to halogen-containing polymers such as PVC when used alone and/or in combination with other flame retardant additives.